1. Field of the Invention
The present invention relates to an image pick-up apparatus and method which takes an image of a subject to generate color video signals of various color spaces.
2. Description of Related Art
FIG. 1 is a view showing a structure of a conventional image pick-up apparatus which uses three mono-color image pick-up elements for three primary colors. A reflected light reflected by a subject 41 is condensed by a lens 3 and is separated into three primary color lights of red (R), green (G) and blue (B) by a dichroic mirror 30. Each light is photoelectrically converted by a mono-color image pick-up element 4 into the primary color video signals R, G or B so as to be outputted. In general, the mono-color image pick-up element 4 is formed of a CCD or an pick-up tube.
In the conventional apparatus, the reflected light can be separated to obtain the video signals of three primary colors, and the color image of high resolution can be obtained from these video signals. However, a dichroic mirror of a high accuracy and three image pick-up elements are required, so that there are problems such that the apparatus has a large size, requires a complicated operation for adjustment and is expensive.
FIG. 2 is a view showing a structure of a conventional image pick-up apparatus using one image pick-up element. A reflected light reflected by the subject 41 is condensed by the lens 3, and is converted into chrominance signals Ye, Mg, Cy and G of four colors by a color image pick-up element 31. In general, the color image pick-up element 31 is provided at the front of the CCD with a color filter 33, in which filters of four colors, i.e., yellow (Ye), magenta (Mg), cyan blue (Cy) and green (G), which are additive complementary colors of red (R), green (G) and blue (B), are arranged in a mosaic form, in order to increase sensitivity, as shown in FIG. 3. The chrominance signals of four colors are converted into primary color video signals R, G and B by a converter 32.
Since the conventional apparatus thus constructed requires only one image pick-up element, sizes and cost can be reduced. However, its resolution is inferior to that of the conventional apparatus shown in FIG. 1, and its color reproducibility is also inferior to the same because the color image pick-up element 31 uses complementary colors.
FIG. 4 is a view showing a structure of a conventional image pick-up apparatus using a coloring device and one mono-color image pick-up element. A reflected light reflected by the subject 41 passes through a coloring device 35 provided with a color filter 36, e.g., of a disk-like form and an electric motor 37 for rotating the color filter 36. The color filter 36 has three regions of red (R), green (G) and blue (B), and can successively provide red light, green light and blue light in accordance with the rotation. These lights are condensed by the lens 3, and are converted by the mono-color image pick-up element 4 into color-field sequential primary color video signals, which are then converted by a converter 34 into the primary color video signals R, G and B.
In the conventional apparatus thus constructed, only one image pick-up element is required, and the resolution and color reproducibility are not inferior. However, it is difficult to reduce the size of the apparatus due to the structure of the coloring device 35 described above.
Since the conventional image pick-up apparatus which takes an image from the reflected light has the above structure, a large and expensive structure is required in order to obtain the image of high resolution, or reduction of the resolution cannot be avoided when the size and cost are to be reduced.
FIG. 5 is a view showing a structure of a conventional image pick-up apparatus using a plurality of color lights and one mono-color image pick-up element. This conventional apparatus uses a primary color light source 1 which sequentially emits three color lights of, e.g., red (R), green (G) and blue (B) to the subject 41. The reflected lights are condensed by the lens 3 to take the image by one mono-color image pick-up element 4. A color-field sequential primary color video signal M obtained in this manner is converted by a converter 42 into primary color video signals R, G and B. A light emitting timing of the primary color light source 1 is controlled by a light emission control device 43.
In the conventional apparatus thus constructed, only one image pick-up element is required, the resolution and color reproducibility are not impaired and reduction of the size is allowed. However, it has such a disadvantage that it is impossible to output signals for the color image display in the color-field sequential type in spite of the fact that the converter 42 is required.
Such an image pick-up apparatus is now available that uses a color CCD and takes an image from a light having passed through a subject such as a color slide or color film. In this conventional image pick-up apparatus, the picture is coarse because the apparatus uses the color CCD. It requires an additional converter for connecting thereto a color display of a color-field sequential type having small size and allowing display of a highly fine picture, which not preferable in view of reduction of the size of the apparatus and the cost.